Contactless control of the flow of water in a sanitary appliance has been increasingly used now, partly in public facilities for hygienic reasons, and partly to reduce water consumption in general.
Prior-art control systems for the contactless operation of washing units are based on an infrared sensor technology. An infrared transmitter is provided, operating with a constant, possibly pulsed radiation power. The transmitter may be adjusted such that the washstand basin is not detected by an infrared receiver operated at an adjustable sensitivity. An object located in the intermediate space, e.g., a body part, especially a hand, is detected.
Such a device has become known in the state of the art from, e.g., CH-A-646,766. This device has an infrared light scanner, which can be operated in a contactless manner and is installed in a water outlet. When an object is introduced into the zone detected by the light scanner, the latter will respond. The detected area in this device is the overlapping area between the transmission lobe and the reception lobe. The transmitted power of the infrared radiator is constant.
The power consumption is relatively high in this device, but this causes no problem in the case of power supply. It is necessary to accurately adjust the detected area at the time of the installation. In addition, it is disadvantageous that the detected area depends on the degree of reflection of the object. Consequently, if an existing background must be masked, one is forced, in the case of a well reflecting background, e.g., a wash basin, to correspondingly limit the range of the system, which leads to an undesired limitation of the detected area.
An electronic control device for the contactless control of the flow of water has become known from CH-A-651,143. This includes two signal transmitters, arranged at spaced locations from one another and operated according to a triangulation process. One particular disadvantage of this device is the fact that it rules out the possibility of miniaturization. The size of the device precludes the accommodation in the water outlet of a washstand appliance. Adjustment operations are to be performed by the installer of the sanitary appliance in this case as well.
The electronic control systems that are currently used for sanitary appliances that can be operated in a contactless manner require, in general, a power supply. This is as a consequence of their high power consumption, which is inherently associated with the system. This makes retrofitting difficult or impossible and, in the case of new installation, it causes installation costs which often exceed those of the control system itself.
The electronic control system of modern sanitary appliances, especially washing units, is operated from a battery for these reasons, and it is completely integrated, together with the battery, in the washstand appliances in an installation-friendly manner.
However, practical battery operation is possible only when the system is able to operate with an extremely low power consumption. Complete integration of the electronic control system, including the battery, in, e.g., a washstand appliance is, in turn, possible, for aesthetic reasons, only if the electronic system and the infrared optical system can be extensively miniaturized.